This invention relates to the production of metal flat products having more than one thickness or which vary in thickness in a controlled manner. It has particular but not necessarily exclusive reference to the manufacture of such plates in titanium, aluminium, nickel, iron or alloys based on such metals.
Titanium alloys are expensive to produce and this is particularly so in the case of titanium alloys used in aero-engine components. Because of the need for extremely high levels of integrity in such parts the quality control required to produce the metal is so high that it adds significantly to the expense. As the parts are frequently of a complex shape it is often necessary to carry out extensive machining of the starting material and these machining operations produce large quantities of waste scrap which has little value.
There is, therefore, a tendency to produce starting components to as near the final nett shape of the products to be produced as is possible. In the manufacture of blades or propellers for use in engines the blades essentially comprise a relatively thin sheet of metal having a thickened end portion which is machined or forged to form a root which is attached to a suitable disc. It would obviously be possible to produce the root by starting with a thick plate and machining away all of the excess material to manufacture the thin sheet leaving the thickened end portion to form the root, the thickened end portion having the thickness of the original plate. Such a machining operation would, however, be very expensive and the yield would be very low.
There has, therefore, been a long felt want for a method to produce a plate of titanium having a thickened end portion and a thinner or tapered body portion. Typically the plate would be 500 mm wide, the thickened portion would be 100 mm long and the main body of the thin portion of the plate would be 11/2 m long.